This commit also allows to pass flags to the new parser in all interfaces and fixes a bug in the parser generator that was causing to inline rules with actions, making them disappear.
Previously every test was building an extension module and
loading it into sys.modules. The tearDown function was thus
not able to clean up correctly, resulting in memory leaks.
With this commit, every test function now builds the extension
module and runs the actual test code in a new process
(using assert_python_ok), so that sys.modules stays intact
and no memory gets leaked.